The invention relates to a process of fermentation wherein the microorganisms or enzymes are recycled into the fermentor after separating therefrom the fermentation filtrate.
Processes for recycling concentrated microorganisms in order to increase the cell concentration in the fermentor are known. Such recycling operation is for instance carried out when making yeast by dehydrating the fermented substrate received from the fermentor together with the yeast by means of centrifuges. The yeast cells are thus separated by the centrifugal force from the spent nutritive medium. The yeast can then be recycled as a 16 to 20% aqueous suspension into the fermentor or can be used otherwise.
However, where the microorganisms are bacteria which are to be recycled, the separation is frequently very difficult because of the size of the microorganisms which is smaller by a full digital point. In this case the water removal must be accomplished by using ultra centrifuges.
If in this case there is still some degree of a closed system of recycling by means of centrifuges, this is definitely no longer possible where the yeasts are separated by vacuum rotary filters. Bacteria can be separated in this manner only after preceding coagulation, which means killing the bacteria.
Another shortcoming of all of these processes is that operation under sterile conditions is very difficult and frequently hardly possible under conditions of industrial use.
It is therefore an object of the invention to provide for a process for recycling and concentrating microorganisms into the fermentor which preferably is carried out under sterile conditions.